1. Field of the Invention
The present invention relates to a lead frame separating device.
2. Prior Art
In a manufacturing process of semiconductor devices, for example, molded lead frames which are stacked in a magazine are removed from the magazine one at a time and supplied to a marking device, where marking is performed on the lead frames.
One example of conventional lead frame separating devices which takes lead frames out of a lead frame magazine is shown in FIG. 4.
A lead frame magazine 2 which accommodates therein lead frames 1 has an opening 2a at the bottom and a vertical groove 2b on the side wall. A bottom plate 3 is placed inside the magazine 2 so that the lead frames 1 are stacked on this bottom plate 3. The bottom plate 3 is fixed to a fixing section of the marking device.
A feed screw 4 and a guide rod 5 are installed in upright positions on one side of the magazine 2. The feed screw 4 is supported by upper and lower supporting plates 6 and 7 so that it is free to rotate. The guide rod 5 is fixed to the supporting plates 6 and 7 at its upper and lower ends.
The output shaft of a motor 8 is connected to the feed screw 4, and this female screw 9 is installed on the feed screw 4. The female screw 9 can slide along the guide rod 5. A lifting member 10 installed beneath the magazine 2 is fastened to the female screw 9. The lifting member 10 is slightly smaller than the opening 2a of the magazine 2. Provided above the magazine 2 are chucking claws 11 which are of a known chucking device. The chucking claws 11 are positioned at a chucking position where the lead frames 1 are picked up. A detection sensor 12 is installed at the chucking position.
When the feed screw 4 is rotated by the motor 8, the lead frames 1 are lifted by the lifting member 10. When the lead frames 1 are raised, the uppermost lead frame 1 is detected by the detection sensor 12. The rotation of the motor 8 is stopped by a signal from the sensor 12, so that the uppermost lead frame 1 is stopped at the chucking position. This lead frame 1 is then chucked by the chucking claws 11.
In the conventional lead frame separating devices described above, the detection position of the detection sensor 12 varies depending upon the lead frames 1. In other words, as a result of variations in the thicknesses of the lead frames 1 and of warping, twisting, etc. of the frames, the detection position can change. In some cases, therefore, proper chucking of the lead frames 1 by the chucking claws 11 is not obtainable. Also, if the type of lead frame 1 being handled is changed, the position of the detection sensor 12 must be adjusted, and this adjustment work takes a considerable amount of time.